1. Field of the Invention
This invention relates to a method for controlling the preparation of blend products from blend stocks boiling at 350.degree. C. or less by predicting chemical, performance, perceptual of physical properties of blend stocks, blend products and/or other refinery or chemical processes using a combination of gas chromatography and mass spectrometry.
2. Description of the Related Art
Refineries and chemical plants typically control blending of various component streams and certain additives through the use of both on-line analyzers and off-line laboratory analyses to provide product quality information. These quality parameters (chemical composition, physical or perceptual or performance properties) are then fed back into linear programs or other blend control software which may be a series of simultaneous equations which predict percentages of refinery streams used to meet certain blend targets. The equations typically are executed more than three times per hour and their output is used to control proportional flow valves to vary the quality of the finished product which can either go to tankage or directly to pipelines and terminals, trucks, or to ship-loading facilities. Multiple on-line analyzers are typically required for blend control.
U.S. Pat. No. 5,223,714 describes a process for controlling the blending of fluids using near-infrared spectroscopy by converting the near-infrared absorbances to signals and mathematically correlating the signal to volume of component.
Gas chromatography has been used to predict physical and performance properties of hydrocarbon mixtures boiling in the gasoline range. Crawford and Hellmuth, Fuel, 1990, 69, 443-447, describe the use of gas chromatography and principal components regression analysis to predict the octane values for gasolines blended from different refinery streams. Japanese laid-open patent application JP 03-100463 relates to a method of estimating the cetane number for fuel oils by separating an oil sample into its components using gas chromatograpy, measuring the signal strength of ion intensities at characteristic masses in the mass spectrum, and correlating these ion intensities to cetane number using multiple regression analysis.
It would be desirable to have a single analyzer means for rapidly measuring the chemical, performance, perceptual or physical properties of blend stocks or blend products and using these properties to control the blending process.